1. Field of the Invention
The present invention concerns a method, a magnetic resonance apparatus and a computer-readable storage medium to display the progress of the acquisition of measurement data from an examination region of a patient during continuous travel of the examination region through the magnetic resonance apparatus.
2. Description of the Prior Art
Magnetic resonance (MR) is a known modality with which images of the inside of an examination subject can be generated. Expressed simply, the examination subject is positioned in a comparably strong, static, homogeneous basic magnetic field (field strengths of 0.2 Tesla to 7 Tesla or more) in a magnetic resonance apparatus so that its nuclear spins orient along the basic magnetic field. Radio-frequency excitation pulses are radiated into the examination subject, that cause the nuclear spins to behave so as to emit magnetic resonance signals that are measured and MR images are reconstructed based thereon. For spatial coding of the measurement data, rapidly-switched (activated) magnetic gradient fields are superimposed on the basic magnetic field. The acquired measurement data are digitized and stored as complex numerical values in a k-space matrix. An associated MR image can be reconstructed from the k-space matrix populated with such values, for example by means of a multidimensional Fourier transformation. The examination subject can be living (for example an animal or a patient) or inanimate (for example a sample or a phantom).
Magnetic resonance apparatuses with a support device (for example a patient bed) that can be automatically driven into and out of a patient receptacle (by means of a drive device) of the magnetic resonance apparatus that is permeated by a magnetic field of the magnetic resonance apparatus are known for the acquisition of magnetic resonance images. Since the patient receptacle frequently has a quite small diameter, the patient is placed on the patient bed outside of the patient receptacle, after which the patient bed can be automatically driven into the patient receptacle by means of the drive device.
The patient or another examination subject is briefly, continuously driven through the magnetic resonance apparatus by means of the support device during the acquisition of the measurement data from an examination region of the patient, or the examination subject. The measured “field of view” (FOV) can be expanded in the direction of the travel direction of the support device by controlling the movement of the support device, so examination regions that are larger in the direction of the travel direction of the support device than the measurement volume of the magnetic resonance apparatus can be examined. For example, whole-body acquisitions of patients can be generated in one measurement pass. Conversely, the measurement volume in which optimally ideal measurement conditions are generated can be limited in the direction of the travel direction of the support device without limiting the total achievable FOV.
Applied techniques for such an acquisition of measurement data can be roughly subdivided into two-dimensional (2D) axial measurements with the travel direction of the support device perpendicular to the readout direction of the measurement data, and three-dimensional (3D) techniques in which the readout direction of the measurement data is oriented parallel to the travel direction of the support device. An overview of such techniques is provided in, for example, the article by Börnert and Aldefeld, “Principles of Whole-Body Continuously-Moving-Table MRI”, Journal of Magnetic Resonance Imaging 28: 1-12 (2008).
Monitoring of the measurement in real time is desirable, in particular given such measurements with continuously moving examination region.
Techniques for generation of overview images in which, for example, the progress of the measurement can be superimposed on planning data are already known in this regard. Such overview images can, for example, be generated within the scope of what are known as prescans. However, the precision of such a monitoring of the progress of a measurement is only low since the actual progress is not monitored, rather a progress “according to plan”.
Furthermore, techniques are known that display current MR data from current or previously acquired measurement data. For this purpose, a current overview image (for example) is calculated using what is known as a “maximum intensity projection” (MIP) from current MR images already reconstructed from the measurement data and is displayed to the operator as a projection image. However, it is disadvantageous that all measurement data must be acquired and processed for such a projection image, which leads to an increased reconstruction time for the current MR images and also the current overview images. The display of such a projection image can therefore normally not be implemented fast enough, in particular not in real time (i.e. simultaneously with the actual progress of the acquisition of the measurement data).